Control systems and methods suitable for use with power production systems and methods

ABSTRACT

Control systems and methods suitable for combination with power production systems and methods are provided herein. The control systems and methods may be used with, for example, closed power cycles as well as semi-closed power cycles. The combined control systems and methods and power production systems and methods can provide dynamic control of the power production systems and methods that can be carried out automatically based upon inputs received by controllers and outputs from the controllers to one or more components of the power production systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Prov. Pat. App. No.62/078,833, filed Nov. 12, 2014, the disclosure of which is incorporatedherein by reference.

FIELD OF DISCLOSURE

The present disclosure relates to control systems and methods, and moreparticularly to control systems and methods that can be integrated withpower production systems and methods.

BACKGROUND

There is a great need for the development of power systems that can meetincreasing consumption needs. While much work is directed to systemsthat do not utilize combustion of fossil fuels, cost factors andavailability of fossil fuels, especially coals and natural gas (as wellas waste hydrocarbons, such as residual oil products), drive a continuedneed for systems configured to combust such fuels, particularly withhigh efficiency and complete carbon capture. To meet these needs, thereis a continued desire for the development of control systems that canprovide for precise control of power systems.

SUMMARY OF THE DISCLOSURE

In one or more embodiments, the present disclosure can provide systemsand methods useful for controlling one or more aspects of a powerproduction system. The control systems particularly can provide controlover one or more of pressure, temperature, flow rate, and streamcomposition of one or more flow streams in a power production system.The control systems can provide for optimum efficiency of the powerproduction system. The control systems further can provide control overaspects of the power production system, such as start-up of the system,shutdown of the system, change of input stream(s) in the system, changeof output stream(s) in the system, handling of operating emergenciesrelated to the system, and any like considerations related to operationof a power production system.

In one or more embodiments, the present disclosure can relate to acontrol system suitable for use in a power production plant. Forexample, the power production plant can be a plant burning a fuel (suchas a hydrocarbon, particularly a hydrocarbon gas) in substantially pureoxygen in a combustor at a pressure of about 12 MPa or greater with anadditional circulating CO₂ stream to produce a combined stream ofcombustion products and circulating CO₂. In some embodiments, the powerproduction can be further characterized by one or more of the followingpoints, which can be combined in any number or order.

The combined stream can be passed through a power producing turbine witha discharge pressure of at least 10 bar.

The turbine exhaust can be cooled in an economizer heat exchange topreheat the circulating CO₂ stream.

The turbine exhaust can be further cooled to near ambient temperature,and condensed water can be removed.

The CO₂ gas stream can be compressed to be at or near the turbine inletpressure using a gas compressor followed by a dense CO₂ pump to form thecirculating CO₂ stream.

Net CO₂ produced in the combustor can be removed at any pressure betweenthe turbine inlet and outlet pressures.

Heat from an external source can be introduced to preheat part of thecirculating CO₂ stream to a temperature in the range 200° C. to 400° C.in order to reduce the temperature difference between the turbineexhaust and the circulating CO₂ stream leaving the economizer heatexchanger to about 50° C. or less.

The fuel gas flow rate can be controlled to provide the required poweroutput from the turbine.

The turbine outlet temperature can be controlled by the speed of the CO₂pump.

The CO₂ compressor discharge pressure can be controlled by recyclingcompressed CO₂ flow to the compressor inlet.

The flow rate of net CO₂ produced from fuel gas combustion and removedfrom the system can be used to control the CO₂ compressor inletpressure.

The difference between the temperature of the turbine exhaust enteringthe economizer heat exchanger and the temperature of the circulating CO₂stream leaving the economizer heat exchanger can be controlled to be ator below 50° C. by controlling the flow rate of a portion of thecirculating CO₂ stream which is heated by an added heat source.

The flow rate of net liquid water and fuel derived impurities removedfrom the system can be controlled by the level in the liquid waterseparator. The oxygen flow rate can be controlled to maintain a ratio ofoxygen to fuel gas flow rate which can result in a defined excess oxygenin the turbine inlet flow to ensure complete fuel gas combustion andoxidation of components in the fuel gas.

The oxygen stream at CO₂ compressor inlet pressure can be mixed with aquantity of CO₂ from the CO₂ compressor inlet to produce an oxidantstream with an oxygen composition of about 15% to about 40% (molar),which can lower the adiabatic flame temperature in the combustor.

The oxidant flow required to produce the required oxygen to fuel gasratio can be controlled by the speed of the oxidant pump.

The discharge pressure of the oxidant compressor can be controlled byrecycling compressed oxidant flow to the compressor inlet.

The inlet pressure of the oxidant compressor can be controlled by theflow rate of diluent CO₂ mixed with the oxygen which forms the oxidantstream.

The ratio of oxygen to CO₂ in the oxidant stream can be controlled bythe flow of oxygen.

The oxygen can be delivered to the power production system at a pressureat least as high as the turbine inlet pressure, and an oxidant streamwith an oxygen composition in the range of about 15% to about 40%(molar) can be desired.

The oxygen to fuel gas ratio can be controlled by the oxygen flow.

The oxygen to CO₂ ratio in the oxidant flow can be controlled by theflow of diluent CO₂ taken from CO₂ compressor discharge.

In any of the embodiments discussed herein, the control of one parameterby a second parameter can particularly indicate that the secondparameter is measured (e.g., with a sensor) or otherwise monitored orthat the second parameter is calculated by a computer based uponadditionally provided information, lookup tables, or presumed values,and a controller initiates a control sequence based upon the measured orcalculated second parameter so that the first parameter is appropriatedadjusted (e.g., by opening or closing of a valve, increasing ordecreasing power to a pump, etc.). In other words, the second parameteris used as a trigger for a controller to implement an adjustment to thefirst parameter.

In one or more embodiments, the present disclosure can provide powerproduction systems that include an integrated control system, which canbe configured for automated control of at least one component of thepower production system. In particular, the control system can includeat least one controller unit configured to receive an input related to ameasured parameter of the power production system and configured toprovide an output to the at least one component of the power productionsystem subject to the automated control. The power production system andintegrated control system can be further defined in relation to one ormore of the following statements, which can be combined in any numberand order.

The power production system can be configured for heat input viacombustion of a fuel.

The power production system can be configured for heat input via anon-combustion heat source.

The power production system can be configured for recycling a stream ofCO₂.

The power production system can be configured for producing an amount ofCO₂ that can be optionally withdrawn from the system, such as beinginput to a pipeline or being utilized for a further purpose, such asenhanced oil recovery.

The power production system can be configured for utilizing a workingfluid that is repeatedly compressed, heated, and expanded.

The integrated control system can include a power controller configuredto receive an input related to power produced by one or more powerproducing components of the power production system.

The power controller can be configured to meet one or both of thefollowing requirements: provide an output to a heater component of thepower production system to increase or decrease heat production by theheater component; provide an output to a fuel valve to allow more fuelor less fuel into the power production system.

The integrated control system can include a fuel/oxidant ratiocontroller configured to receive one or both of an input related to fuelflow rate and an input related to oxidant flow rate.

The fuel/oxidant ratio controller can be configured to meet one or bothof the following requirements: provide an output to a fuel valve toallow more fuel or less fuel into the power production system; providean output to an oxidant valve to allow more oxidant or less oxidant intothe power production system.

The integrated control system can include a pump controller configuredto receive an input related to temperature of an exhaust stream of aturbine in the power production system and to provide an output to apump upstream from the turbine to increase or decrease flow rate of astream exiting the pump.

The integrated control system can include a pump suction pressurecontroller configured to receive an input related to suction pressure ona fluid upstream from a pump in the power production system and toprovide an output to a spillback valve that is positioned upstream fromthe pump.

The pump suction pressure controller is configured to meet one or bothof the following requirements: cause more of the fluid or less of thefluid to spill back to a point that is further upstream from thespillback valve; cause more of the fluid or less of the fluid to beremoved from the power production system upstream from the pump.

The integrated control system can include a pressure regulationcontroller configured to receive an input related to pressure of anexhaust stream of a turbine in the power production system and toprovide an output to a fluid outlet valve and allow fluid out of theexhaust stream and optionally to provide an output to a fluid inletvalve and allow fluid into the exhaust stream.

The integrated control system can include a water separator controllerconfigured to receive an input related to the amount of water in aseparator of the power production system and to provide and output to awater removal valve to allow or disallow removal of water from theseparator and maintain the amount of the water in the separator within adefined value.

The integrated control system can include an oxidant pump controllerconfigured to receive an input related to one or both of a mass flow ofa fuel and a mass flow of an oxidant in the power production system andcalculate a mass flow ratio of the fuel and the oxidant.

The oxidant pump controller can be configured to provide an output tothe oxidant pump to change the power of the pump so as to affect themass flow ratio of the fuel and the oxidant in the power productionsystem.

The integrated control system can include an oxidant pressure controllerconfigured to receive an input related to the pressure of an oxidantstream downstream from an oxidant compressor and to provide an output toan oxidant bypass valve to cause more oxidant or less oxidant to bypassthe compressor.

The integrated control system can include an oxidant pressure controllerconfigured to receive an input related to the pressure of an oxidantstream upstream from an oxidant compressor and to provide an output to arecycle fluid valve to cause more recycle fluid or less recycle fluidfrom the power production system to be added to the oxidant streamupstream from the oxidant compressor. In particular, the recycle fluidcan be a substantially pure CO₂ stream.

The integrated control system can include a dilution controllerconfigured to receive an input related to one or both of the mass flowof an oxidant and the mass flow of an oxidant diluent stream and tocalculate a mass flow ratio of the oxidant and the oxidant diluent.

The dilution controller can be configured to provide an output to anoxidant entry valve to allow more oxidant or less oxidant to enter thepower production system so that the mass flow ratio of the oxidant tothe oxidant diluent is within a defined range.

The integrated control system can include a compressor suction pressurecontroller configured to receive an input related to suction pressure ofa fluid upstream from a compressor in the power production system and toprovide an output to a spillback valve that is positioned downstreamfrom the compressor and that causes more of the fluid or less fluid tospill back to a point that is upstream from the compressor.

The integrated control system can include a pump speed controllerconfigured to receive an input related to suction pressure upstream fromthe pump and to provide an output to the pump to increase or decreasepump speed.

The integrated control system can include a side flow heat controllerconfigured to receive an input related to a calculated mass flowrequirement for a side flow of a high pressure recycle stream in thepower production system and to provide an output to a side flow valve toincrease or decrease the amount of the high pressure recycle stream inthe side flow.

The power production system can comprise: a turbine; a compressordownstream from the turbine and in fluid connection with the turbine; apump downstream from the compressor and in fluid connection with thecompressor; and a heater positioned downstream from the pump and influid connection with the pump and positioned upstream from the turbineand in fluid connection with the turbine. Optionally, the powerproduction system can include a recuperator heat exchanger.

In one or more embodiments, the present disclosure can provide methodsfor automated control of a power production system. In particular, themethod can comprise operating a power production system comprising aplurality of components that include: a turbine; a compressor downstreamfrom the turbine and in fluid connection with the turbine; a pumpdownstream from the compressor and in fluid connection with thecompressor; and a heater positioned downstream from the pump and influid connection with the pump and positioned upstream from the turbineand in fluid connection with the turbine. Further, operating the powerproduction system can include using one or more controllers integratedwith the power production system to receive an input related to ameasured parameter of the power production system and provide an outputthat automatically controls at least one of the plurality of componentsof the power production system. In further embodiments, the methods caninclude one or more of the following steps, which can be combined in anynumber and order.

The output can be based upon a pre-programmed, computerized controlalgorithm.

The operating can include input of heat via combustion of a fuel.

The operating can include input of heat via a non-combustion heatsource.

The operating can include recycling a stream of CO₂.

The operating can include producing an amount of CO₂ that can beoptionally withdrawn from the system, such as being input to a pipelineor being utilized for a further purpose, such as enhanced oil recovery.

The operating can include utilizing a working fluid that is repeatedlycompressed, heated, and expanded.

The operating can include using a controller to receive an input relatedto power produced by the power production system and direct one or bothof the following actions: provide an output to the heater to increase ordecrease heat production by the heater; provide an output to a fuelvalve of the power production system to allow more fuel or less fuelinto the power production system.

The operating can include using a controller to receive one or both ofan input related to fuel flow rate and an input related to oxidant flowrate and to direct one or both of the following actions: provide anoutput to a fuel valve of the power production system to allow more fuelor less fuel into the power production system; provide an output to anoxidant valve of the power production system to allow more oxidant orless oxidant into the power production system.

The method operating can include using a controller to receive an inputrelated to temperature of an exhaust stream of the turbine and providean output to the pump upstream from the turbine to increase or decreaseflow rate of a stream exiting the pump.

The operating can include using a controller to receive an input relatedto suction pressure on a fluid upstream from the pump and provide anoutput to a spillback valve that is positioned upstream from the pump.In particular, one or both of the following requirements can be met: thecontroller causes more of the fluid or less of the fluid to spill backto a point that is further upstream from the spillback valve; thecontroller causes more of the fluid or less of the fluid to be removedfrom the power production system upstream from the pump.

The operating can include using a controller to receive an input relatedto pressure of an exhaust stream of the turbine and provide an output toa fluid outlet valve and allow fluid out of the exhaust stream andoptionally provide an output to a fluid inlet valve and allow fluid intothe exhaust stream.

The operating can include using a controller to receive an input relatedto the amount of water in a separator included in the power productionsystem and provide and output to a water removal valve to allow ordisallow removal of water from the separator and maintain the amount ofthe water in the separator within a defined value.

The operating can include using a controller to receive an input relatedto one or both of a mass flow of a fuel and a mass flow of an oxidantintroduced to the power production system and calculate a mass flowratio of the fuel and the oxidant. In particular, the controller canprovide an output to an oxidant pump to change the power of the pump soas to affect the mass flow ratio of the fuel and the oxidant in thepower production system.

The operating can include using a controller to receive an input relatedto the pressure of an oxidant stream downstream from an oxidantcompressor and provide an output to an oxidant bypass valve to causemore oxidant or less oxidant to bypass the compressor.

The operating can include using a controller to receive an input relatedto the pressure of an oxidant stream upstream from an oxidant compressorand to provide an output to a recycle fluid valve to cause more recyclefluid or less recycle fluid to be added to the oxidant stream upstreamfrom the oxidant compressor. In particular, the recycle fluid can be asubstantially pure CO₂ stream.

The operating can include using a controller to receive an input relatedto one or both of the mass flow of an oxidant and the mass flow of anoxidant diluent stream and to calculate a mass flow ratio of the oxidantand the oxidant diluent. In particular, the controller can be configuredto provide an output to an oxidant entry valve to allow more oxidant orless oxidant to enter the power production system so that the mass flowratio of the oxidant to the oxidant diluent is within a defined range.

The operating can include using a controller to receive an input relatedto suction pressure of a fluid upstream from the compressor and providean output to a spillback valve that is positioned downstream from thecompressor and that causes more of the fluid or less fluid to spill backto a point that is upstream from the compressor.

The operating can include using a controller to receive an input relatedto suction pressure upstream from the pump and to provide an output tothe pump to increase or decrease pump speed.

The operating can include using a controller to receive an input relatedto a calculated mass flow requirement for a side flow of a high pressurerecycle stream and provide an output to a side flow valve to increase ordecrease the amount of the high pressure recycle stream in the sideflow.

BRIEF SUMMARY OF THE FIGURES

Having thus described the disclosure in the foregoing general terms,reference will now be made to accompanying drawings, which are notnecessarily drawn to scale, and wherein:

FIG. 1 is a schematic of a power production system including componentsof a control system according to embodiments of the present disclosure,said control components being particularly configured for thermalcontrols;

FIG. 2 is a schematic of a power production system including componentsof a control system according to further embodiments of the presentdisclosure, said control components being additionally configured forcontrol over the heat source;

FIG. 3 is a schematic of a power production system including componentsof a control system according to further embodiments of the presentdisclosure, said control components being particularly configured forcontrol over elements of a direct fired power production system;

FIG. 4 is a schematic of a power production system including componentsof a control system according to further embodiments of the presentdisclosure, said control components being particularly configured forcontrol over further elements of a direct fired power production system;

FIG. 5 is a schematic of a power production system including componentsof a control system according to further embodiments of the presentdisclosure, said control components being particularly configured forcontrol over further elements of a direct fired power production system,including removal of excess mass from the power production system;

FIG. 6 is a schematic of a power production system including componentsof a control system according to further embodiments of the presentdisclosure, said control components being particularly configured forcontrol over further elements of a direct fired power production system,including removal of excess mass from the power production system; and

FIG. 7 is a schematic of a power production system including componentsof a control system according to further embodiments of the presentdisclosure, said control components being particularly configured forcontrol over heat input to the power production system.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art. As used in this specification and the claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontext clearly dictates otherwise.

In one or more embodiments, the present disclosure provides systems andmethods for control of power production. The control systems and methodscan be utilized in relation to a wide variety of power productionsystems. For example, the control systems can be applied to one or moresystems wherein a fuel is combusted to produce heat to a stream that mayor may not be pressurized above ambient pressure. The control systemslikewise can be applied to one or more systems wherein a working fluidis circulated for being repeatedly heated and cooled and/or for beingrepeatedly pressurized and expanded. Such working fluid can comprise oneor more of H₂O, CO₂, and N₂, for example.

Examples of power production systems and methods wherein a controlsystem as described herein can be implemented are disclosed in U.S. Pat.No. 9,068,743 to Palmer et al., U.S. Pat. No. 9,062,608 to Allam et al.,U.S. Pat. No. 8,986,002 to Palmer et al., U.S. Pat. No. 8,959,887 toAllam et al., U.S. Pat. No. 8,869,889 to Palmer et al., U.S. Pat. No.8,776,532 to Allam et al., and U.S. Pat. No. 8,596,075 to Allam et al,the disclosures of which are incorporated herein by reference. As anon-limiting example, a power production system with which a controlsystem as presently described may be utilized can be configured forcombusting a fuel with O₂ in the presence of a CO₂ circulating fluid ina combustor, preferably wherein the CO₂ is introduced at a pressure ofat least about 12 MPa and a temperature of at least about 400° C., toprovide a combustion product stream comprising CO₂, preferably whereinthe combustion product stream has a temperature of at least about 800°C. Such power production system further can be characterized by one ormore of the following:

The combustion product stream can be expanded across a turbine with adischarge pressure of about 1 MPa or greater to generate power andprovide a turbine discharge steam comprising CO₂.

The turbine discharge stream can be passed through a heat exchanger unitto provide a cooled discharge stream.

The cooled turbine discharge stream can be processed to remove one ormore secondary components other than CO₂ to provide a purified dischargestream. The purified discharge stream can be compressed to provide asupercritical CO₂ circulating fluid stream.

The supercritical CO₂ circulating fluid stream can be cooled to providea high density CO₂ circulating fluid (preferably wherein the density isat least about 200 kg/m³).

The high density CO₂ circulating fluid can be pumped to a pressuresuitable for input to the combustor.

The pressurized CO₂ circulating fluid can be heated by passing throughthe heat exchanger unit using heat recuperated from the turbinedischarge stream.

All or a portion of the pressurized CO₂ circulating fluid can be furtherheated with heat that is not withdrawn from the turbine discharge stream(preferably wherein the further heating is provided one or more of priorto, during, or after passing through the heat exchanger).

The heated pressurized CO₂ circulating fluid can be recycled into thecombustor (preferably wherein the temperature of the heated, pressurizedCO₂ circulating fluid entering the combustor is less than thetemperature of the turbine discharge stream by no more than about 50°C.).

The presently disclosed control systems can be particularly useful inrelation to power production methods such as exemplified above becauseof the need for providing precise control over multiple parameters inrelation to multiple streams, such parameters needing precise control toprovide desired performance and safety. For example, in one or moreembodiments, the present control systems can be useful in relation toany one or more of the following functions.

The present control systems can be useful to allow for differentialspeed control of a power producing turbine and a compressor that isutilized to compress a stream that is ultimately expanded through theturbine. This is an advantage over conventional gas turbines wherein thecompressor and the turbine are mounted on the same shaft. Thisconventional configuration makes it impossible to operate the compressorat a variable speed. Constant rotational speed and inlet conditionsyield a substantially constant mass throughput into the compressor andtherefore the turbine. This can be affected through the use of inletguide vanes, which restrict the airflow entering the compressor andthereby lower the mass throughput. According to the present disclosure,the use of a pump between the compressor and the turbine provides forsignificant levels of control of the power production system. Thisallows for decoupling of the mass throughput of the compressor-pumptrain and the shaft speed of the turbine-compressor-generator train.

The present control systems can be useful to control the inlet and/oroutlet pressure of a turbine expanding a heated gas stream. The heatedgas stream can be predominately CO₂ (by mass).

The present control systems can be useful to control an outlettemperature of a turbine.

The present control systems can be useful to control operation of apower production system with a CO₂ compression means to raise the CO₂pressure from a turbine exhaust volume to the pressure of a turbineinlet volume so that these pressures are maintained.

The present control systems can be useful to control removal of the netCO₂ formed from carbon in a combustor fuel gas at any point in the CO₂compression means from turbine exhaust pressure to turbine inletpressure.

The present control systems can be useful to control operation of apower production system wherein a hot turbine exhaust is cooled in aneconomizer heat exchanger while heating a recycle high pressure CO₂stream to ensure the heat recovery from the cooling turbine exhaustprovides the optimum flow of heated high pressure CO₂ recycle to acombustor at the highest possible temperature.

The present control systems can be useful to optimize heat input to arecycle CO₂ stream (for example, at a temperature of about 400 ° C. orless) from an external heat source to control the temperature differencein an economizer heat exchanger below a temperature of 400 ° C. tomaximize the quantity of recycle CO₂ which can he heated against acooling turbine exhaust stream and minimize the hot end temperaturedifference of the economizer heat exchanger.

The present control systems can be useful to control the fuel flow to acombustor to ensure that the combustion products when mixed with a highpressure heated recycle CO₂ stream form the inlet gas stream to aturbine at the required temperature and pressure.

The present control systems can be useful to control the oxygen flow toa combustor to give a required excess O₂ concentration in a turbineoutlet stream to ensure complete combustion of a fuel.

The present control systems can be useful to control operation of apower production system so that a turbine exhaust stream leaving aneconomizer heat exchanger can be further cooled by ambient cooling meansto maximize the condensation of water formed in the combustion processand reject the net water production from fuel gas combustion togetherwith other fuel or combustion derived impurities.

In one or more embodiments, a power production suitable forimplementation of a control system as described herein can be configuredfor heating via methods other than through combustion of a fossil fuel.As one non-limiting example, solar power can be used to supplement orreplace the heat input derived from the combustion of a fossil fuel in acombustor.

Other heating means likewise can be used. In some embodiments, any formof heat input into a CO₂ recycle stream at a temperature of 400° C. orless can be used. For example, condensing steam, gas turbine exhaust,adiabatically compressed gas streams, and/or other hot fluid streamswhich can be above 400° C. may be utilized.

In some embodiments, it can be particularly useful to control a turbineoutlet temperature at a maximum value that is fixed by the maximumallowable temperature of an economizer heat exchanger being utilized.Such control can be based on the turbine inlet and outlet pressures andthe heat exchanger operating hot end temperature difference.

Control systems of the present disclosure can be defined by one or morefunctions wherein a parameter (e.g., a measured parameter and/or acalculated parameter) can be linked to one or more executable actions.The executable actions can include one or more actions that regulate aflow of a fluid in the system, such as through opening and closing ofone or more valves. As non-limiting examples, measured parameters in acontrol system according to the present disclosure can include a fluidflow rate, a pressure, a temperature, a liquid level, a fluid volume, afluid composition, and the like. A measured parameter can be measuredusing any suitable device, such as thermocouples, pressure sensors,transducers, optical detectors, flow meters, analytical equipment (e.g.,UV-VIS spectrometers, IR spectrometers, mass spectrometers, gaschromatographs, high performance liquid chromatographs, and the like),gauges, and similar devices. Calculated parameters in a control systemaccording to the present disclosure can include, for example, powerconsumption of a compressor (e.g., a CO₂ compressor), power consumptionof a pump (e.g., a CO₂ pump), power consumption of a cryogenic oxygenplant, fuel heat input, a pressure drop (e.g., a pressure drop in a heatexchanger) for one or more fluid streams, a temperature differential(e.g., a temperature difference at a heat exchanger hot end and/or heatexchanger cold end), a turbine power output, a generator power output,and system efficiency. A calculated parameter may be calculated, forexample, by a computerized supervisory control system based on measuredparameters.

Embodiments of the present disclosure are illustrated in FIG. 1, whichillustrates a control system that may be used particularly for a closedpower cycle. The control system is particularly useful in systems andmethods where direct control over the amount of heat entering thesystem, for instance in solar applications, is not required. In thisconfiguration, a working fluid is circulated through a heater 12, aturbine 10 connected to a generator 11, a first heater/cooler 16, acompressor 30, a second heater/cooler 18, and a pump 20. Optionally, arecuperator heat exchanger 50 can be included so that heat in workingfluid stream 101 b exiting turbine 10 can be recuperated into theworking fluid stream 101 g to exit as working fluid stream 101 h that isfurther heated by the heater 12.

Heat entering the power production system in heater 12 is added to theworking fluid, which is preferably as a high pressure (e.g., about 10bar or greater, about 20 bar or greater, about 50 bar or greater, about80 bar or greater, about 100 bar or greater, about 150 bar or greater,about 200 bar or greater, or about 250 bar or greater) to provide a highpressure, heated working fluid stream 101 a. This stream passes to theturbine 10 and is expanded to a lower pressure to exit as working fluidstream 101 b. Parameter check point 13 is configured downstream from theturbine 10 and upstream from the first heater/cooler 16 (and optionallyupstream from the recuperator heat exchanger 50 if present) and includesa temperature sensor, thermocouple, or the like. Controller 2 (which canbe characterized as a pump controller) directs and/or gathers one ormore temperature readings (which readings can be continuous or periodic)at parameter check point 13. So as to maintain a substantially constanttemperature at parameter check point 13, controller 2 directs poweradjustments as necessary for pump 20. For example, controller 2 cancontrol the speed of pump 20 in response to the temperature reading atparameter check point 13. In this manner, controller 2 can be configuredto maintain a desired temperature in working fluid stream 101 bindependent of the amount of heat that is being introduced into thesystem in heater 12, and likewise independent of the inlet temperatureof turbine 10. This is beneficial in that pump 20 can be specificallycontrolled to deliver the correct mass flow of working fluid at thecorrect pressure as dictated by the inlet temperature to the turbine 10as indicated by the amount of heat introduced in heater 12.

Such dynamic control can affect one or more further parameters in thepower production system illustrated in FIG. 1. For example, changes inthe flow rate through pump 20 causes changes in the suction pressureimmediately upstream from the pump in working fluid stream 101 f. Inorder to maintain desired controllability of pump 20, the suctionconditions of the pump must remain as constant as possible within thepredetermined range. Second heater/cooler 18 can be useful to maintainthe suction temperature at pump 20 at a desired value. So as to maintaina substantially constant suction pressure for pump 20, controller 3(which can be characterized as a pump suction pressure controller) canbe configured to monitor a pressure sensor, transducer, or the likepositioned at parameter check point 23, and controller 3 can utilizepressure readings taken therefrom to control a spillback valve 31, whichcan be configured to allow more or less fluid from working fluid stream101 e to spill back to parameter check point 44, which can be at anyposition in working fluid stream 101 c. Controller 3 thus essentiallycan be configured to control the amount of recirculation flow aroundcompressor 30 via the spillback valve 31. As such, pressure at parametercheck point 23 can be increased by reducing fluid flow through spillbackvalve 31 and can be decreased by increasing fluid flow through thespillback valve. As fluid is spilled back into working fluid stream 101c, it can also be desirable to maintain a substantially constantpressure in working fluid streams 101 b and 101 c. Accordingly,parameter check point 13 can likewise include a pressure sensor,transducer, or the like. The temperature sensor and the pressure sensorcan be configured in the same parameter check point, or differentparameter check points can be utilized in working fluid stream 101 b forthe respective sensors.

Because parameter check point 13 is in fluid communication withparameter check point 44 and parameter check point 43, the respectivepressures at points 13, 44, and 43 may differ substantially only due toinherent pressure losses through equipment and piping. Controller 4 canbe configured to monitor a pressure sensor, transducer, or the likepositioned at parameter check point 43, and controller 4 can beconfigured to control valve 41 so as to allow fluid from working fluidstream 101d into, or out of, the system in order to maintain asubstantially constant pressure at parameter check point 44. As such,parameter check point 44 can include a pressure sensor, transducer, orthe like, which can be monitored by controller 4 if desired.

Alternatively, because parameter check points 43 and 44 are in fluidcommunication, the measured pressure at parameter check point 43 can beconsidered to be substantially identical to the pressure at parametercheck point 44. Valve 41 can be configured to remove and/or add fluid tothe working fluid stream in order to maintain the desired pressure. Insome embodiments, there can be two valves instead of the single valve41—a first valve (i.e., a fluid outlet valve) configured to allow fluidout to a lower pressure sink, and a second valve (i.e., a fluid inletvalve) configured to allow fluid in from a higher pressure source.

In some embodiments, the illustrated system can be controlled such thatvalve 41 is either absent or is not utilized, and controller 3 caninstead operate to substantially prevent surging by the compressor 30.In such embodiments, controller 2 can still operate to managetemperature at parameter check point 13, and the control look can be acompletely closed loop, which configuration can be particularly usefulfor indirectly heated power production cycles. For example, in one ormore embodiments, heater 12 can be configured for provision of solarheating at or above a defined heat level, and the power productionsystem can thus be substantially self-regulating to produce as muchpower as possible with dynamic response to changes in the solar input.Such configuration could likewise be maintained if additional heat for afurther source was continuously or intermittently added in heater 12.

In the illustrated system of FIG. 1, compressor 30 receives its inletworking fluid stream from the turbine 10, and its outlet working fluidstream is delivered ultimately to the pump 20. The compressor 30 can beshaft-mounted on the turbine 10, and the working conditions of thecompressor may be substantially unchanged based on the control of theturbine exhaust conditions. .

Although controller 2, controller 3, and controller 4 are illustratedand discussed as being separate controllers, it is understood that therespective controllers can be configured as part of a larger unit. Forexample, a single control unit may include a plurality of subunits thatcan be individually connected with their designated parameter checkpoints and their controlled devices (e.g., the pump 20, the spillbackvalve 31, and the valve 41). Moreover, the control units can beconfigured substantially as subroutines in an overall controller (e.g.,a computer or similar electronic device) with a plurality of inputs anda plurality of outputs that are designated for the respective parametercheck points and controlled devices.

In embodiments wherein recuperative heat exchanger 50 is included,control of temperature at parameter check point 13 can be particularlyimportant. By maintaining the temperature at parameter check point 13 ator substantially near a steady state value, the temperature profiles inthe recuperative heat exchanger 50 can remain substantially constant aswell. At a minimum, such control scheme is beneficial because of thereduction or elimination of thermal cycling of the piping, heatexchangers, and other high temperature equipment utilized in the system,which in turn can significantly increase component lifetimes.

Embodiments of the present disclosure are illustrated in FIG. 2, whichshows a power production system that is substantially identical to thepower production system illustrated in FIG. 1. In the system of FIG. 2,a further controller 1 (which can be characterized as a powercontroller) is included and can be configured for monitoring a varietyof values and directing a number of control commands.

In one or more embodiments, controller 1 can be configured to measureand/or receive measurements in relation to the power output of generator11. In some embodiments, controller 1 can be configured to direct heatinput via heater 12 to generate the required power. Thusly, if poweroutput at generator 11 is above or below the desired output, heat inputvia heater 12 can be decreased or increased to deliver the desired poweroutput. Similarly, monitoring of power output with controller 1 canenable dynamic changes to the heat input so that a substantiallyconstant power output can be provided. As a non-limiting example, whensolar heating is utilized for heater 12, the power output at generator11 can be utilized as a trigger so that, for example, more mirrors maybe aimed at a collection tower to increase heat output when power outputdrops below a defined level and/or when the power output is insufficientto meet a predefined heating algorithm, such as wherein power output maybe automatically increased at a time of day when usage is expected to beincreased. As a further non-limiting example, a plurality of heatsources can be utilized wherein a first heat source can be utilizedprimarily, and a second heat source can be automatically brought onlinewhen power output at the generator 11 is insufficient. For example,solar heating may be combined with combustion heating with one being theprimary heat source and the other being the secondary heat source tosupplement the primary heat source.

As more or less heat is added to the system, the turbine inlettemperature will change and, after expansion through the turbine, thetemperature at parameter check point 13 will change. As such, one ormore of the control functions described above in relation to FIG. 1likewise can be implemented in the system as illustrated in FIG. 2.

Embodiments of the present disclosure are further illustrated in FIG. 3,which illustrates a control system that may be used particularly for asemi-closed power cycle. The control system is particularly useful insystems and methods where the cycle is a direct fired oxy-fuel cycleburning a carbonaceous fuel with oxygen. As illustrated at least twocomponents that can be combined to provide an exothermic reaction areintroduced to the system through valve 14 and valve 71. The componentsare shown as being introduced directly to turbine 10; however, in one ormore embodiments, the components may be introduced to a reactor, such asa combustor. In some embodiments, turbine 10 is a multi-stage componentincluding a reaction or combustion chamber upstream from a turbine. InFIG. 3, the portion of element 10 below the dashed line can be acombustion chamber, and the portion of element 10 above the dashed linecan be a turbine. As a non-limiting example, valve 14 can be configuredfor metering a fuel, such as natural gas or other fossil fuel, and valve71 can be configured for metering an oxidant, such as air orsubstantially pure oxygen (e.g., at least 95%, at least 98%, at least99%, or at least 99.5% pure oxygen).

In the system exemplified in FIG. 3, controller 1 can be configured tomonitor the power output of generator 11. Based upon the measured poweroutput, controller 1 controls fuel valve 14 to allow more fuel or lessfuel into the power production system. As more fuel or less fuel isadded to the power production system, controller 7 (which can becharacterized as a fuel/oxidant ratio controller) compares the fuel flowrate at parameter check point 15 to the oxidant flow rate at parametercheck point 72, and controller 7 commands the oxidant valve 71 to allowmore oxidant or less oxidant therethrough in order to maintain theprescribed ratio of fuel to oxygen.

Reaction (e.g., combustion) products pass through the turbine 10 (or theturbine section of a combination reactor/turbine) and exit as a turbineexhaust stream. As an example, when natural gas and oxygen are meteredthrough valve 14 and valve 71, the main products in the turbine exhauststream will be H₂O and CO₂. The turbine exhaust stream can pass througha recuperator heat exchanger 50 (although such component is optional)and then pass through the first heater/cooler 16. The turbine exhauststream is then treated in water separator 60 where water can be takenoff through valve 61. A substantially pure CO₂ stream exits the top ofthe separator 60 and is passed through compressor 30 (with a fractionbeing drawn off through valve 41. A compressed recycle CO₂ streamexiting compressor 30 is passed through the second heater/cooler 18 andthen pump 20 to provide a high pressure recycle CO₂ stream, which can bepassed back to the turbine 10 (optionally passing through therecuperator heat exchanger 50 to be heated with heat withdrawn from theturbine exhaust stream). A substantially pure CO₂ stream can comprise atleast 95% by weight, at least 97% by weight, at least 98% by weight, atleast 99% by weight, or at least 99.5% by weight CO₂.

As illustrated in FIG. 3, the control system used with the exemplarypower production system includes controller 2, controller 3, andcontroller 4, which can function substantially identically as describedabove in relation to the systems of FIG. 1 and FIG. 2. In addition,controller 6 (which can be characterized as a water separatorcontroller) is utilized to monitor water level in separator 60, whichcan include one or more sensors suitable for providing a water leveloutput that can be read by controller 6. Based on the water level signalreceived, controller 6 can direct valve 61 to open at the correctintervals and durations to maintain the water level in the separator 60at a desired level. Although measurement is referenced in relation to awater level, it is understood that volume, mass, or other parameters maybe utilized to provide the signal to controller 6.

Additional embodiments of the present disclosure are illustrated in FIG.4, which illustrates a control system that may be used particularly fora semi-closed power cycle utilizing an artificial air source. Thecontrol system is particularly useful in systems and methods where thecycle is a direct fired oxy-fuel cycle burning a carbonaceous fuel withoxygen. Controller 1 again monitors the power output of generator 11 andmeters fuel input through valve 14 accordingly.

As illustrated in FIG. 4, fuel and oxidant enter the combustion sectionof dual combustor/turbine 10, and a turbine exhaust stream exits theturbine section. The turbine exhaust stream can pass through arecuperator heat exchanger 50 (although such component is optional) andthen pass through the first heater/cooler 16. The turbine exhaust streamis then treated in water separator 60 where water can be taken offthrough valve 61. A substantially pure CO₂ stream exits the top of theseparator 60 and is passed through compressor 30 (with a fraction beingdrawn off through valve 41). A compressed recycle CO₂ stream exitingcompressor 30 is passed through the second heater/cooler 18 and thenpump 20 to provide a high pressure recycle CO₂ stream, which can bepassed back to the dual combustor/turbine 10 (optionally passing throughthe recuperator heat exchanger 50 to be heated with heat withdrawn fromthe turbine exhaust stream).

In this configuration, oxidant enters through valve 111 and passesthrough union 114, where CO₂ can be combined with the oxidant. Theoxidant stream (optionally diluted with the CO₂ stream) passes throughheater/cooler 22, is pressurized in compressor 90, passes throughheater/cooler 24, and is finally passed through in pump 80. Controller 8(which can be characterized as an oxidant pump controller) measures theratio between the mass flow of the fuel (read at parameter check point26) and the mass flow of the oxidant (read at parameter check point 82).Based upon the calculated ratio, controller 8 can direct variable speedpump 80 to change the power of the pump and allow the delivery ofoxidant in the correct mass flow to maintain the desired oxidant to fuelratio at the required pressure. In this manner, the amount of oxidantsupplied to the power production system is consistently at the correctflow rate and correct pressure for passage into the dualcombustor/turbine 10. If, for example, the pressure at parameter checkpoint 82 were to rise due to back pressure from the combustor/turbine10, controller 8 can be configured to command pump 80 to operate at adifferent speed suitable to provide the correct pressure and oxidantmass flow. Based upon a pressure reading taken at parameter check point93, controller 9 (which can be characterized as an oxidant pressurecontroller) can direct spillback valve 91 to decrease or increase thepressure at parameter check point 93 by allowing more or less fluid tospill back (or be recycled) to a point upstream from the compressor 90(particularly between union 114 and heater/cooler 22. Pressure likewisecan be monitored at parameter check point 102 (which pressurecorresponds to the suction of compressor 90). Based upon this pressure,controller 100 (which can be characterized as an oxidant pressurecontroller) can direct valve 103 to divert none or a portion of thefluid upstream of compressor 30 to union 114 so as to maintain asubstantially constant pressure at parameter check point 102. Thesubstantially pure CO₂ stream diverted through valve 103 can be utilizedto dilute the oxidant, and controller 100 likewise can be configured toincrease or decrease flow through valve 103 to provide the desireddilution. Mass flow of the CO₂ stream provided through valve 103 can bemeasured at parameter check point 113, and the mass flow of the oxidantprovided through valve 111 can be measured at parameter check point 112.Controller 110 (which can be characterized as a dilution controller) canbe configured to calculate the ratio of the flows at check points 112and 113, and can be configured to direct valve 111 to allow more oxidantor less oxidant to enter the system so as ensure that the correct ratiois maintained.

In one or more embodiments, a control system according to the presentdisclosure can be configured to specifically provide for mass controlacross a wide range of pressures. Low pressure mass control (e.g., atambient pressure to about 10 bar, to about 8 bar, or to about 5 bar) canbe achieved similarly to the description of controller 4 above. Inparticular, controller 4 can be configured to open or close valve 41 torelieve excess mass from the power production system. For example, in asystem utilizing a recycle CO₂ stream as a working fluid and combustinga fossil fuel, excess CO₂ can be formed. To maintain the correct massbalance in the system, all or a portion of the formed CO₂ can be drawnoff through valve 41. The amount of fluid drawn though valve 41 forpurposes of mass control can be calculated based upon the knownstoichiometry of the combustion reaction, and controller 4 can beconfigured to control mass flow through valve 41 accordingly. Ifdesired, one or more sensors can be utilized to measure and/or calculatefluid mass downstream from the combustor and/or to measure and/orcalculate fluid mass ratio between a stream between the combustor andthe valve 41 in relation to a stream that is downstream from thecompressor 30 and/or the pump 20.

In the embodiment illustrated in FIG. 5, controller 3 and controller 4as described above are absent, and further controllers are provided inorder to release the excess mass from the power production system atsubstantially the same pressure as the outlet pressure of the compressor30 (which is substantially identical to the suction of pump 20). Asdescribed above, the speed of pump 20 is controlled by the exhausttemperature of the turbine 10 via controller 2. In the embodimentexemplified in FIG. 5, however, suction pressure of compressor 30 iscontrolled. In particular, parameter check point 54 can include apressure sensor, and controller 35 (which can be characterized as acompressor suction controller) can be configured to open and close valve31 based upon the pressure at the suction of the compressor 30 asmeasured at parameter check point 54. If the pressure at parameter checkpoint 54 begins dropping, controller 35 can be configured to open valve31 and allow fluid to spill back to a point upstream from parametercheck point 54 (spillback going to parameter check point 44 in theillustrated embodiment) and raise the pressure at parameter check point54. If the pressure at parameter check point 54 begins increasing,controller 35 can be configured to close valve 31 so as to reduce theamount of fluid spilling back and lower the pressure at parameter checkpoint 54.

In addition to controlling the speed of pump 20, the suction pressure ofthe pump can also be controlled. In particular, the pressure read atparameter check point 23 can be utilized by controller 75 (which can becharacterized as a pump speed controller), which can be configured toopen and close valve 88. Accordingly, the suction pressure of pump 20 iscontrolled by removing excess fluid from the power production system atvalve 88, which in turn provides for maintaining the desired systempressure.

In the embodiment illustrated in FIG. 6, the power control system isconfigured similarly to the construction illustrated in FIG. 5 butwithout the use of valve 88. In this illustrated embodiment, thecompressor 30 operates on suction pressure control as described inrelation to FIG. 5, and pump 20 also operates on suction pressurecontrol. In particular, the pressure read at parameter check point 23can be utilized by controller 75, which can be configured to adjust thespeed of pump 20 to maintain controlled suction conditions and output atcorrect pressure dictated by the further parameters of the combustioncycle. In addition, temperature taken from parameter check point 13 canagain be used by controller 2; however, the controller 2 can beconfigured to direct flow through valve 115 to control the temperatureof the exhaust from turbine 10. By allowing more fluid out of the powerproduction system through valve 115 (or keeping more fluid in the powerproduction system), the inlet pressure (and therefore mass flow) throughturbine 10 can be controlled, and the outlet temperature of turbine 10can be likewise controlled.

In one or more embodiments, a power system shown in FIG. 7 can comprisea turbine 10 coupled to an electric generator 11. A fuel stream ismetered through valve 14, and oxygen is metered through valve 71, andthe fuel is combusted with the oxygen in combustor 10. The fuel andoxygen are mixed with heated, high pressure recycle CO₂ stream 120leaving the economizer heat exchanger 50. Combustion gases pass to theturbine 10 b. The turbine discharge stream is cooled in the economizerheat exchanger 50 against the high pressure recycle CO₂ stream 119 andis further cooled to near ambient temperature in the first heater/cooler16. In some embodiments, the first heater/cooler 16 can be an indirectheat exchanger using for example cooling water or it can be a directcontact heat exchanger which both cools the turbine exhaust stream andcondenses water. The near ambient temperature stream enters waterseparator 60 which discharges the condensed liquid water stream throughvalve 61. The stream can include fuel or combustion derived impuritieswhich are an oxidized state, such as SO₂ and NO₂. In the case of adirect contact cooler the unit acts as a combined gas cooler gas/watercontactor and liquid phase separator. The recycled CO₂ stream 116 entersCO₂ recycle compressor 30 where its pressure is raised (e.g., from about30-70 bar to about 80 bar). The compressor 30 is provided with a recycleCO₂ line 45 with a valve 31 to reduce the pressure and return a portionof the compressor flow to the suction at point 44. The net CO₂ product,which contains all the carbon derived from the fuel gas stream followingoxidation in the turbine combustor, is vented from the compressor asstream through valve 41. The net CO₂ product can be delivered atpressure from the compressor suction to the pump discharge. The recycledCO₂ stream exiting the compressor 30 is cooled to near ambienttemperature in second heater/cooler 18. The density increases totypically about 0.7 kg/liter to about 0.85 kg/liter. The densesupercritical CO₂ is pumped to typically 320 bar in a multistagecentrifugal pump 20. The recycled CO₂ stream 119 exiting pump 20 entersthe economizer heat exchanger 50.

A portion 119 a of the recycled CO₂ stream exiting pump 20 is heated inheat exchanger 56 against a heating stream 53, which can be from anysource, such as heat withdrawn from an air separation unit. This stream119 a is heated typically to a temperature of about 200° C. to about400° C. The heated stream is then passed into the heat exchanger 50 atan intermediate point and remixed with the high pressure recycle CO₂stream 119. The system is controlled by control valves which regulatethe fluid flows. The system is provided with sensors which measure flowrates, pressures, temperatures and gas compositions. These measurementscan be fed, for example, to a digital control system which regulates thepower plant using control algorithms together with stored supervisorycontrol programs. The output from the control system regulates thedegree of opening of the control valves plus the speed of the pump 20and other system functions. The objective is to achieve defined highefficiency operation at any required power output, optimum start-upconditions, controlled ramp rates either up or down, shutdown andresponds to system malfunctions. Although such digital control systemand control algorithms are mentioned in relation to the system of FIG.7, it is understood that such disclosure applies equally to any furtherembodiments described herein, including embodiments described inrelation to and of FIG. 1 through FIG. 6 an FIG. 8.

The functional control of the system can be defined by the links betweenthe variables measured by sensors and the response of the particularcontrol valve. One or more embodiments of control systems that can beutilized in relation to any embodiments disclosed herein include thefollowing.

The fuel flow rate through valve 14 can be controlled by the electricitydemand imposed on the electric generator 58.

The speed of pump 20 can be used to control its discharge flow rate. Inparticular, the flow rate set point can be varied to maintain a definedturbine outlet temperature.

The outlet pressure of the CO₂ compressor 30 can be maintained at aconstant defined value by varying the set point of the compressorrecycle flow control valve 31.

Venting of CO₂ produced in the power production cycle can be controlledby the flow control valve 41. The set point of this flow controller canbe varied to maintain a constant inlet pressure to the CO₂ compressorand the turbine discharge. In some embodiments wherein venting throughvalve 41 takes place at the discharge of compressor 30, the controlsystem can be configured to vary the flow through valve 41 and throughthe recycle valve 31.

The quantity of recycle high pressure CO₂ that is heated by the addedheat source in heat exchanger 56 can be controlled by the flow controlvalve 42 and controller 17 (which can be characterized as a side flowheat controller). The set point of the CO₂ flow is controlled tominimize the temperature difference at the hot end of heat exchanger 50between the high pressure CO₂ recycle stream 120 and the turbine exhauststream at point 13 below 50° C.

The discharge of condensed water together with fuel and combustionderived oxidized impurities can be controlled by maintaining a constantwater level in the water separator 60 or in the sump of the alternativedirect contact cooler. In the latter case, the excess water isdischarged while the main water discharge flow is pumped through acooling water heat exchanger and introduced into the top of the directcontact cooler above the packing layer.

With reference to FIG. 5, the flow rate of oxygen to the combustor canbe controlled by the flow control valve 111. The set point of the flowcontroller can be varied to maintain a defined ratio of oxygen to fuelgas which will ensure typically 1% excess oxygen above thestoichiometric value to ensure complete fuel combustion plus oxidationof any fuel derived impurities. In order to control the adiabatic flametemperature of the integral turbine combustor, it can be useful todilute the oxygen with a quantity of CO₂ to produce a CO₂ plus O₂ gasmixture having between 15% and 40%, typically 25% (molar) O₂concentration. The oxygen stream can be diluted with a CO₂ stream takenfrom the inlet line of the CO₂ compressor 30. The withdrawn CO₂ passesthrough flow control valve 103 and enters union 114 which, in someembodiments, can be a static mixer. The set point of the flow controllerfor valve 91 can be adjusted by the supervisory computer program tomaintain a constant pressure at point 102. The set point of the oxygeninlet flow control valve 111 can be adjusted to maintain a fixed ratioof oxygen to carbon dioxide flow entering the mixer 114. The mixedoxidant stream passes through heater/cooler 22. The cooled oxidantstream enters the oxidant compressor 90 where it is compressed typicallyto the range of about 90 bar to about 120 bar pressure. The set point offlow control valve 91 can be varied to control the discharge pressure ofthe oxidant compressor 90. The oxidant compressor 90 can operate withfixed inlet and outlet pressures. The discharge from compressor 90 canbe cooled to near ambient temperature in heater/cooler 24. Its densityis increased to the range of, for example, about 0.6 kg/liter to about0.75 kg/liter. The dense supercritical oxidant stream 82 is pumped totypically 320 bar pressure in the multi-stage centrifugal pump 80. Thehigh pressure discharge stream exiting pump 80 enters the economizerheat exchanger 50 where it is heated by a portion of the heat releasedfrom the cooling turbine discharge stream. The flow rate of oxidant canbe controlled by adjusting the speed of the oxidant pump 80. The flowrate set point can be adjusted to maintain a defined ratio of oxygen tofuel gas which will provide typically 1% excess oxygen above thequantity required for stoichiometric fuel gas combustion to ensurecomplete fuel gas combustion plus oxidation of any fuel derivedimpurities.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing description.Therefore, it is to be understood that the invention is not to belimited to the specific embodiments disclosed and that modifications andother embodiments are intended to be included within the scope of theappended claims. Although specific terms are employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation.

1-40. (canceled)
 41. A power production system with an integratedcontrol system configured for automated control of at least onecomponent of the power production system, the power production systemcomprising: a heater; a power producing generator; and at least onecontroller; wherein the at least one controller is configured to receivean input downstream from the heater and provide an output that isconfigured to adjust a flow of a fuel to the heater and thereby controla heat output by the heater; and wherein the at least one controller isconfigured to receive the same input or a different input downstreamfrom the heater and provide an output to control a flow of a stream of aworking fluid to the heater.
 42. The power production system of claim41, wherein the at least one controller includes a power controllerconfigured to receive an input related to power produced by the powerproducing generator and provide the output that is configured to adjusta flow of a fuel to the heater and thereby control the heat output bythe heater.
 43. The power production system of claim 42, wherein thepower controller is configured to meet one or both of the followingrequirements: provide an output to the heater to increase or decreaseheat production by the heater; provide an output to a fuel valve toallow more fuel or less fuel to be passed to the heater.
 44. The powerproduction system of claim 41, wherein the at least one controllerincludes a pump controller configured to receive an input related to atemperature of an exhaust stream downstream from the heater and providean output to a pump to control the flow of the stream of the workingfluid to the heater.
 45. The power production system of claim 41,wherein the at least one controller includes a fuel/oxidant ratiocontroller configured to receive one or both of an input related to fuelflow rate into the heater and an input related to oxidant flow rate intothe heater and provide one or both of the following: provide an outputto a fuel valve to allow more fuel or less fuel to be passed to theheater; provide an output to an oxidant valve to allow more oxidant orless oxidant to be passed to the heater.
 46. The power production systemof claim 41, wherein the at least one controller includes an oxidantpump controller configured to receive an input related to one or both ofa mass flow of the fuel and a mass flow of an oxidant passed to theheater and calculate a mass flow ratio of the fuel and the oxidant, andwherein the oxidant pump controller is configured to provide an outputto an oxidant pump to change the power of the pump so as to affect themass flow ratio of the fuel and the oxidant passed to the heater. 47.The power production system of claim 41, wherein the at least onecontroller includes an oxidant pressure controller configured to receivean input related to the pressure of an oxidant stream upstream from anoxidant compressor and to provide an output to cause more of the workingfluid or less of the working fluid to be added to the oxidant streamupstream from the oxidant compressor.
 48. The power production system ofclaim 41, wherein the working fluid is substantially pure CO₂.
 49. Thepower production system of claim 41, wherein the heater is a combustor.50. The power production system of claim 41, wherein the heater is asolar heater.
 51. The power production system of claim 41, wherein theheater is configured for providing heating from a fluid stream at atemperature above 400° C.
 52. A method for automated control of a powerproduction system, the method comprising: combusting a fuel with anoxidant in a heater in the presence of a working fluid and exhaustingfrom the heater an exhaust stream; producing power using the exhauststream; using at least one controller to receive at least one inputdownstream from the heater and provide an output that adjusts a flow ofone or both of the fuel and the oxidant to the heater and therebycontrols an amount of heat in the exhaust stream; and using the at leastone controller to receive the same input or a different input downstreamfrom the heater and provide an output that controls a flow of a streamof the working fluid to the heater.
 53. The method of claim 52, whereinthe at least one controller includes a power controller that receives aninput related to power produced by the power producing generator andprovides and output that adjusts a flow of a fuel to the heater andthereby controls the amount of heat in the exhaust stream.
 54. Themethod of claim 53, wherein the power controller is configured to meetone or both of the following requirements: provide an output to theheater to increase or decrease heat production by the heater; provide anoutput to a fuel valve to allow more fuel or less fuel to be passed tothe heater.
 55. The method of claim 52, wherein the at least onecontroller includes a pump controller that receives an input related toa temperature of the exhaust stream downstream from the heater andprovides an output to a pump that controls the flow of the stream of theworking fluid to the heater.
 56. The method of claim 52, wherein the atleast one controller includes a fuel/oxidant ratio controller thatreceives one or both of an input related to fuel flow rate into theheater and an input related to oxidant flow rate into the heater andprovides one or both of the following: provides an output to a fuelvalve to allow more fuel or less fuel to be passed to the heater;provides an output to an oxidant valve to allow more oxidant or lessoxidant to be passed to the heater.
 57. The method of claim 52, whereinthe at least one controller includes an oxidant pump controller thatreceives an input related to one or both of a mass flow of the fuel anda mass flow of the oxidant passed to the heater and calculates a massflow ratio of the fuel and the oxidant, and wherein the oxidant pumpcontroller provides an output to an oxidant pump to change the power ofthe pump so as to affect the mass flow ratio of the fuel and the oxidantpassed to the heater.
 58. The method of claim 52, wherein the at leastone controller includes an oxidant pressure controller that receives aninput related to the pressure of an oxidant stream upstream from anoxidant compressor and provides an output to cause more of the workingfluid or less of the working fluid to be added to the oxidant streamupstream from the oxidant compressor.
 59. The method of claim 52,wherein the working fluid is substantially pure CO₂.